I remember Fiio has stated that, I do not recall the exact sentences, but the main point being below:
Due to large fragmentation of Android devices having different versions of Android as well as different OEM implementations, also older devices having Micro-USB port and newer devices having USB-C port, it is difficult to have official support for Android.
Q5/Q1mk I/Q1 mkII supports most Android devices but it has often occurred that after software updates, devices which previously supports OTG DAC no longer supports. The opposite may also happen: Devices which previously did not support OTG DAC may suddenly support it after updates. Some Android devices with USB-C may drain the phone's battery to charge the DAC when they are connected, some won't.
Due to such fragmentation, support for Android OTG is a little bit of hit-or-miss scenario and because of this Fiio does not advertise their DACs to support Android while they actually DO support, in most cases.
The scenario is different for Apple iOS because the fragmentation is not there and with proper Apple MFi certification they can easily advertise official iOS support without any worries.
I personally have used my Nexus 6P and OnePlus 5 with Fiio Q1 mkI connected with aftermarket USB-C to Micro OTG cable with no issues. Can't speak of Q5 though.
Hope this helps.
Hamster